1. Field of the Invention
The present invention relates to an exposure apparatus and a device manufacturing method using the same.
2. Description of the Related Art
An exposure apparatus is an apparatus that transfers a pattern of an original plate (reticle or the like) onto a photosensitive substrate (e.g., wafer, glass plate, and the like, where the surface thereof is coated with a resist layer) via a projection optical system in a lithography step included in manufacturing steps for a semiconductor device, a liquid crystal display device, and the like. In particular, there is a flip chip mounting method as a method for mounting a semiconductor device on a wafer. In the semiconductor device manufacturing processes corresponding to the flip chip mounting method, a step of forming a solder ball on a device (chip) is included. Furthermore, there is a plating method as a method for forming a solder ball. In the plating method, a part of a resist, which comes into contact with an electrode, formed on a conductive film needs to be peeled off in advance in order to bring the conductive film formed on a wafer into contact (conduction) with the electrode of a plating device. For example, when the resist is a negative resist, exposure light is prevented from irradiating the outer peripheral region of a wafer upon exposure by an exposure apparatus. For realizing this, U.S. Pat. No. 6,680,774 discloses an apparatus in which a light shielding plate for shielding the outer peripheral region from light during exposure is arranged above the surface of a wafer. Furthermore, Japanese Patent Laid-Open No. 2011-233781 discloses a lithography apparatus in which a light shielding plate is arranged on a plane optically conjugate to a wafer plane instead of on a wafer. In the lithography apparatus disclosed in Japanese Patent Laid-Open No. 2011-233781, a light shielding plate having a circular-arc at its edge is positionally controlled by a first driving unit that rotationally drives the light shielding plate about an axis parallel to the optical axis of an illumination system and a second driving unit that linearly drives the light shielding plate within a plane perpendicular to the optical axis in order to define an exposure region corresponding to a peripheral shot region located in the outer peripheral region. With the aid of positioning control, the distance (light-shielding width) from the outer periphery of a wafer to the borderline of the outer peripheral region which is shielded against light becomes constant for each peripheral shot region.
However, when a light shielding plate is arranged above the surface of a wafer as disclosed in U.S. Pat. No. 6,680,774, the light shielding plate needs to be retracted at the time of each wafer exchange, which is undesirable in terms of spacing for disposing a drive mechanism for driving the light shielding plate and throughput. On the other hand, even when a light shielding plate is arranged on a plane optically conjugate to a wafer plane as disclosed in Japanese Patent Laid-Open No. 2011-233781, a drive mechanism for driving the light shielding plate is still arranged within the apparatus. For example, in order to shield any desired position on the peripheral shot region from light by means of dual-axis drive such as rotation drive and linear drive, it is required that the second driving unit for linearly driving a light shielding plate is mounted above the first driving unit for rotationally driving the light shielding plate about the optical axis. Consequently, it becomes difficult to dispose a sensor or mounting parts when considering the fact that the position of the light shielding plate is directly measured within the drive mechanism. In addition, it is preferable that the rotating center of the first driving unit matches the optical axis from the viewpoint of optimization of drive amount for the improvement in throughput. At this time, the transmission of rotation to the light shielding plate needs to be performed from the first driving unit due to limitation on the arrangement of the light shielding plate near the rotating center serving as an optical path. However, the transmission of rotation via a gear, a belt, or the like may lead to mechanical deterioration due to wear or the like. Such mechanical deterioration directly affects on the positioning accuracy of light shielding. In particular, a mechanical deterioration caused by long-time use of a lithography apparatus may lead to change in light-shielding position on a wafer, resulting in an adverse effect on the products themselves. In order to avoid such circumstances, it is contemplated that the positioning accuracy of light shielding is inspected by periodically exposing and developing a test wafer but a certain apparatus down time and man-hour of inspection are required.